Today i was bored. So i rebuild my GK71 tweeter. New secondary has 14 turns of 2mm enameled wire on a 55mm cardboard pipe. Somewhere between 20 and 30Mhz. The choke has the same dimensions. I used flat copper for the Anode, the ground connection an the feedback. Power supply is a MOT with bridge rectifier + some microwave caps.
I am quite satisfied with this result
Greetings
Re: GK71 HFVTTC 30cm Flames Thomas W, Sun May 27 2012, 10:16PM
Thanks, Tom Williamson! It is not that hard to build one.
Here is a new video getting 30cm flames! I just increased the topload capacitance and added some chemicals on the breakoutpoint. The ruler is 30cm in lenght...
Looks good and its a massive output for a tube running with cold plates. I got a good deal of tubes that size, maybe its time for a quick hfvttc as you did :)
@Weston: Yes. I don´t know, i never tried to vary the distance between the 2 coils. But i think it does not matter.
@Pinkamena: That is true! xD
@Mads Barnkob: Thanks! :) It stays cold for about 30 seconds or so, than it gets slightly dark red. "maybe its time for a quick hfvttc as you did :)" Try it! It is very simple and fun!
Thanks. Grid 1 is for the feedback. Grid 2 is on supply +. (11,7k) Grid 3 is on ground. I could try to connect G1 and G2...
Greetings
Re: GK71 HFVTTC 30cm Flames zrg, Sun Jun 03 2012, 02:49PM
Well, that's a really well tuned flame discharge generator, I must say. Being inspired by OP, remade my old GK-71 tweeter. Parameters are quite similar to OP's: ~30 MHz frequency, MOT with full-bridge rectifier and 2uf capacitance, 11k from + to grid 2, 10k from grid 1 to cathode, three power ceramic doorknob USSR caps (K15Y-1) 15 pf each in series, from secondary end to grid 1, as a capacitive feedback. Plate becomes red-orange after ~20-30 sec run, probably because of no tuning at all
Re: GK71 HFVTTC 30cm Flames Tetris, Sun Jun 03 2012, 03:19PM
Did you put salt on the electrode? Why is the arc orange? heh. first thing that came to mind was: oh wow this is high current. second thing: if you are amish that inherited a lot of money, and wants to sort of become more with the world, you'd make this. looks like a candle, but much more dangerous and made of plasma.
but that is one badass coil! there is no other way to say it!
Re: GK71 HFVTTC 30cm Flames RateReducer, Sun Jun 03 2012, 05:53PM
Thanks, zrg! :) Nice coil. I would like to have ceramic pipes like you use them... The cardboard pipes i use get deformed because of the heat.
Thanks, HighVoltageChick! No, i do not use salt. It is potassium sodium tartrate. (Stuff to breed crystals xD)
That´s a good comparison! Even more realistic with sulfur on the breakout point! Nice bluish flames + smell .
Re: GK71 HFVTTC 30cm Flames Marko, Sat Jun 16 2012, 02:18PM
Wow, that has to be one insane plasma tweeter. Any attempts at audiomodulation yet?
I'm wondering if this tube is just right for such a tweeter because it's rated for such a low frequency (20Mhz), which probably means it has quite significant output capacitance which helps loading the coil.
Also, how long are the flames without any dopings on the breakout point?
Marko
Re: GK71 HFVTTC 30cm Flames PhilGood, Sat Jun 16 2012, 05:34PM
@Marko: Thanks. Yes i tried to modulate it with a transformer + amplifier... It worked but not very loud. You can find a video on my YT channel. I am currently working on another tweeter with audio modulation. The flames are about 20cm max. without dopings.
@PhilGood: Thanks. It is just the basic tweeter circuit. You can find many of the in the net. I already posted the grid configuration. If you have any questions - message ;)
Greetings
Re: GK71 HFVTTC 30cm Flames Thomas W, Tue Jun 19 2012, 06:16AM
Re: GK71 HFVTTC 30cm Flames Dr. Dark Current, Tue Jun 19 2012, 09:52AM
Sorry to jump in, I've done some measurements on the GK 71 in the past and it absolutely needs forced air cooling at full plate dissipation, and the plate is not supposed to get red. So if you want your tube to last, direct some air flow onto it and don't let the plate get red.
Re: GK71 HFVTTC 30cm Flames Thomas W, Tue Jun 19 2012, 03:17PM
indeed it is the GK71, this is my first valve project and i have no clue what values i should use for resistors, capacitors and types ect D: i have heard that valves are rather forgiving so.... c: